JPH0411111B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a coextruded multilayer sheet, and more specifically, a coextruded multilayer sheet suitable for forming deep drawn containers with excellent rigidity and gas barrier properties. It provides sheets.

(Prior art) Linear polyester in general, and polyethylene terephthalate (hereinafter referred to as PET) in particular, has attracted attention as a material for various containers including bottles due to its excellent mechanical and chemical properties. -Represented by the method described in Publication No. 5107
Demand for deep-drawn containers made from PET sheets is also increasing as they have excellent rigidity and gas barrier properties.

However, improvements in packaging technology and expansion of packaging applications require the addition of higher functionality to PET containers, such as further improvement in gas barrier properties.

As a means of improving the gas barrier properties of such PET containers, we have developed a partially saponified resin of ethylene/vinyl acetate copolymer (hereinafter referred to as EVOH), which is a material with even better gas barrier properties than PET, or a resin based mainly on EVOH. A coextruded multilayer sheet of vinyl resin and PET has been proposed, and the technology is being actively developed, but it has not yet been put into practical use.

(Problem to be solved by the invention) Although the effects of high-performance sheets made by combining PET/EVOH are predicted to be highly evaluated, the main reason why their practical application has been delayed is The problem lies in the adhesion between the two.

While PET has a highly crystalline and non-polar molecular structure, EVOH has a polar molecular structure with hydroxyl groups with large molecular cohesive energy, making direct adhesion of PET and EVOH impossible. .

Therefore, in order to form a multilayer PET/EVOH sheet, an adhesive layer is indispensable in the middle, but an adhesive suitable for forming such a sheet has not yet been found. Of course it's just PET
If the purpose is to adhere EVOH, adhesives based on acid anhydride group-containing polyolefin, epoxy group-containing polyolefin, or polyurethane have already been put into practical use.

In addition, the development of adhesives based on polyamides and polyesters is actively progressing, but adhesives for coextruded multilayer sheets intended for secondary processing such as deep drawing must not only have adhesive strength but also suitability for melt extrusion. It goes without saying that secondary processability, such as aptitude for stretching and stretching, and even transparency, if necessary, are required.

However, in order to improve adhesion, it is a general tendency that molding processability decreases as the degree of modification advances, such as various copolymerizations and polymer alloys. The difficulty of balancing PET/EVOH
This can be said to be one of the major reasons why the practical application of highly functional multilayer sheets has been delayed.

(Means for Solving the Problems) The present inventors have solved these problems, and have developed a product that has excellent rigidity and gas barrier properties, can maintain transparency if necessary, and can also be used for deep drawing processing, etc. PET layer/adhesive layer/ that also has secondary stretch processability
In order to develop a coextruded multilayer sheet with an EVOH layer as a basic unit, we have arrived at the present invention as a result of intensive research, especially regarding the adhesive layer.

That is, the present invention is a multilayer sheet having a structure in which a two-layer adhesive layer is provided between PET and EVOH, and the adhesive layer on the PET side is made of sulfonate group-containing polyester, and the side on the EVOH side is made of polyamide. This is a coextruded multilayer sheet with special characteristics.

Furthermore, the sulfon group-containing polyester is PET copolymerized with 0.5 to 10 mol% of sodium sulfoisophthalic acid and/or sodium sulfo terephthalic acid, and the polyamide contains 5 to 30% by weight of a nylon 66 component. A coextruded multilayer sheet characterized by being made of a polyamide comprising:

A sheet with such a structure has strong adhesion between each layer, and at the same time, when using an adhesive layer with a composition range limited to the present invention, it has good sheet formability, deep drawing workability, and transparency. Excellent multilayer sheets can be stably obtained.

The PET used in the present invention is a polyester whose main repeating unit is ethylene terephthalate, and the amount of phthalic acid, isophthalic acid, hexahydrophthalic acid, naphthalene dicarboxylic acid, adipic acid, and sebacin is 10 mol% or less of the total acid component. It is possible to use dicarboxylic acids such as acids, polycarboxylic acids such as trimellitic acid and pyromellitic acid, or oxyacids such as p-oxybenzoic acid as the acid component.
1,2-propanediol in an amount of up to mol%;
Dihydric alcohols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, cyclohexanedimethanol, trimethylolpropane,
Polyhydric alcohols such as triethylolpropane and pentaerythritol can be used as the alcohol component. PET like this
is obtained by a conventional melt polycondensation reaction, and if necessary, the degree of polymerization can be further increased by a solid phase polymerization reaction.

The EVOH used in the present invention has the trade name “EVAL”
It is a crystalline polymer obtained by saponifying a random copolymer of ethylene/vinyl acetate, as represented by the following: It has polar hydroxyl groups and exhibits extremely excellent gas barrier properties due to its large molecular cohesive energy.

The sulfon group-containing polyester, which is one of the constituent components of the adhesive layer of the present invention, includes sodium sulfoisophthalic acid as a part of the acid component in the polyester.
It can be easily obtained by a conventional melt polycondensation reaction using sodium sulfoterephthalic acid, and when a polymer with a high degree of polymerization is required, a solid phase polymerization reaction can also be used.

If the amount of the copolymerized sodium sulfoisophthalic acid and/or sodium sulfioterephthalic acid is 0.5 mol % or more, sufficient adhesion to PET and polyamide can be obtained.

In addition, when the amount of copolymerization exceeds 10 mol%, the adhesive force reaches saturation, and no further effect can be expected, and at the same time, the hygroscopic effect of the sulfon group occurs.
It also does not give good results to the gas barrier properties of EVOH. The basic physical properties of the sulfonate group-containing polyester are as follows:
It is desirable that the polyester be close to PET, but this can be solved by using PET containing sulfone groups as the polyester. Similarly, polyamides which are other constituent components of the adhesive layer of the present invention include polycapramide,
Selected from polylaurinlactam, polyhexamethyleneadipamide, poly11-aminoundecanoic acid, etc.

Although these may be used alone, as a copolymer, or as a mixture, a nylon 6/66 copolyamide containing 5 to 30% by weight of a nylon 66 component is particularly preferred.

The composition of the multilayer sheet according to the present invention is PET/sulfonate group-containing polyester/polyamide/
It is obtained by extruding EVOH as a basic unit through a multilayer die using four extruders dedicated to each resin.
It can have a seven-layer structure of polyamide/EVOH/polyamide/sulfon group-containing polyester/PET, or a multilayer structure of more than that if necessary.

(Function) In the present invention, a sulfon group-containing polyester and a polyamide that have been copolymerized and modified within a range that does not impair the excellent extrusion characteristics, processability, and polymer properties of PET and polyamide are arranged between PET and EVOH. The excellent mutual adhesion of PET/sulfonated polyester/polyamide and polyamide/EVOH is used to make a coextruded multilayer sheet suitable for deep drawing applications, and the multilayer sheet obtained by the present invention is After heating in the range of 100 to 150°C, a container with excellent rigidity and gas barrier properties can be easily formed by vacuum forming or pressure forming.

(Example) Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 A melt polycondensation reaction was carried out by a conventional method using 98.2 mol% of terephthalic acid, 1.8 mol% of 5-sodiumsulfoisophthalic acid, and 100 mol% of ethylene glycol in a mixed solvent of equal weight of phenol/tetrachloroethane. A sulfon group-containing polyester having an intrinsic viscosity of 0.70 measured at 20°C was obtained.

On the other hand, nylon 6.6 contains 15% by weight of nylon 66 component and has a relative viscosity of 4.5 when measured at 25°C in 96% concentrated sulfuric acid.
66 copolymerized polyamide was prepared. Intrinsic viscosity
Measured at 190℃ for 10 minutes with 1.0 PET and 2160g load.
EVOH with MI (melt index) value of 1.40g
Prepare [Eval EP-F manufactured by Kuraray Co., Ltd.], dry these materials thoroughly, and extrude them from a multilayer die using four extruders for each purpose to form PET.
(320μ) / Sulfon group-containing PET (20μ) / Copolyamide polyamide (20μ) / EVOH (80μ) / Copolymer polyamide (20μ) / Sulfone group-containing PET (20μ) /
A sheet of PET (320μ) with a thickness of 800μ and consisting of seven layers was obtained. The sheet had a uniform thickness with no uneven thickness between each layer, and although there was some cloudiness due to EVOH, it was a transparent sheet, and the layers were so firmly adhered that they could not be separated. This sheet was heated at 130° C. for 5 seconds and then vacuum-formed into a cup with a diameter of 100 mm and a depth of 40 mm, resulting in a uniformly stretched transparent product.

Comparative Example 1 According to the method of Example 1, but without using the sulfon group-containing polyester, PET
(340μ) / Copolymer polyamide (20μ) / EVOH
(80μ)/Copolyamide (20μ)/PET (340μ)
A sheet with a thickness of 800 μm and having a five-layer structure was obtained.

The resulting sheet has poor adhesion and easily peels off at the adhesive interface of PET/copolyamide, making it difficult to form a stable sheet, and the container also peels off from the flange after deep drawing, making it impractical. It was hot.

(Effects of the Invention) As is clear from the Examples and Comparative Examples, the coextruded multilayer sheet that satisfies the requirements of the present invention has excellent productivity and secondary processability, and containers formed from this sheet have good rigidity and gas resistance. An extremely practical product with excellent barrier properties can be obtained.

Claims (1)

[Claims] 1. Adhesion consisting of two layers between polyethylene terephthalate or a polyester resin layer mainly composed of polyethylene terephthalate and a partially saponified resin of ethylene/vinyl acetate copolymer or a vinyl resin layer mainly composed of this. 1. A coextruded multilayer sheet comprising an adhesive layer, wherein the polyester resin layer side of the adhesive layer is made of sulfon group-containing polyester, and the vinyl resin layer side is made of polyamide. 2. Claim 1, characterized in that the sulfon group-containing polyester is polyethylene terephthalate copolymerized with 0.5 to 10 mol% of sodium sulfoisophthalic acid and/or sodium sulfophoterephthalic acid. coextruded multilayer sheet. 3 Polyamide contains 5-30% by weight of nylon 66 component
The coextruded multilayer sheet according to claim 1, characterized in that the coextruded multilayer sheet is made of a polyamide containing polyamide.